Many thanks, Sue. I can now add Mary's and Madie's exact birth date to their records. It is strange that Mary T doesn't appear in any records after her birth, but Madie is easy to trace via census and, later a marriage to Colin C Turner. I have Madie Jane Clayton Turner's death in Weston-Super-Mare.
With the search for Marion Martha/Edith Marion Clayton Gibson, now that I have her younger sister, Elizabeth Ann Clayton Ketterson's obituary, I know that Marion died before her as only two of Elizabeth Ann's siblings are mentioned as family (Henry living in Durban, and Isabella living in London).
Thank you again everyone who has so kindly helped with my Clayton research.